CHAPEL HILL, N.C. — The N.C.A.A. did not dispute that the University of North Carolina was guilty of running one of the worst academic fraud schemes in college sports history, involving fake classes that enabled dozens of athletes to gain and maintain their eligibility.

But there will be no penalties, the organization said, because no rules were broken.

In a ruling that caused head-scratching everywhere except Chapel Hill, the N.C.A.A. announced on Friday that it could not punish the university or its athletics program because the “paper” classes were not available exclusively to athletes. Other students at North Carolina had access to the fraudulent classes, too.

Noting that distinction, the panel that investigated the case “could not conclude that the University of North Carolina violated N.C.A.A. academic rules,” the N.C.A.A. said in a statement.

The N.C.A.A.’s determination was a major victory for North Carolina after years of wrangling and uncertainty. The athletic department — one of the most high-profile and lucrative ones in the country, and a source of deep pride in the state — could have faced severe penalties, including the loss of championships in men’s basketball, its signature sport.

The N.C.A.A.’s committee on infractions concluded it lacked the power to punish the university under the rules of the N.C.A.A., an association that expects members to govern themselves and establishes a wide berth when it comes to determining what qualifies as academic progress.

“N.C.A.A. policy is clear,” said Greg Sankey, the commissioner of the Southeastern Conference, who led the panel. “The N.C.A.A. defers to its member schools to determine whether academic fraud occurred and, ultimately, the panel is bound to making decisions within the rules set by the membership.”

Carol L. Folt, the university’s chancellor, welcomed the ruling, pointing to the process the university underwent with its accrediting body as well as reforms it instituted internally. “I believe we have done everything possible to correct and move beyond the past academic irregularities and have established very robust processes to prevent them from recurring,” she said.

According to a university-commissioned investigation, North Carolina had for nearly two decades offered a “shadow curriculum” of fake classes into which athletes were steered. It appeared to be a stark subversion of the N.C.A.A.’s central tenet that college athletics are a mere component of education.

The scheme involved nearly 200 laxly administered and graded classes — frequently requiring no attendance and just one paper — over nearly two decades in the African and Afro-American Studies Department. Their students were disproportionately athletes, especially in the lucrative, high-profile sports of football and men’s basketball. They were mostly administered by a staff member named Deborah Crowder. In many cases, athletes were steered to the classes by athletics academic advisers.

The scandal was so serious that the university’s accreditation body briefly placed the university on probation.

In its notice of allegations, which is the N.C.A.A. equivalent of a lawsuit or an indictment, the N.C.A.A.’s enforcement staff pointed to the high enrollment of athletes in the classes — nearly half, according to the university-commissioned investigation led by Kenneth L. Wainstein — and emails in which advisers requested spots for athletes. It charged North Carolina with a “lack of institutional control” resulting in violations of bylaws governing extra benefits to athletes and ethical conduct.

U.N.C. had contended that the case was fundamentally academic in nature, and that athletics staffers were at most tangential to it. The university cited instances in which similar misconduct was alleged at Auburn and Michigan, and the N.C.A.A. did not act.

“The fact that the courses did not meet our expectations,” Mark Merritt, the university’s general counsel, said in a call with reporters, “doesn’t make them fraudulent.”

In a tone that seemed begrudging at times, the panel accepted that reasoning.

“While student-athletes likely benefited from the so-called ‘paper courses’ offered by North Carolina, the information available in the record did not establish that the courses were solely created, offered and maintained as an orchestrated effort to benefit student-athletes,” Sankey said.

Sankey added that his panel was “troubled by the university’s shifting positions about whether academic fraud occurred on its campus,” but he said the infractions committee was powerless to punish North Carolina for courses the university offered to any member of the general student body.

The panel said it had to take North Carolina at its word.

Critics of the N.C.A.A. cited the ruling as another exhibit in their case that the college sports establishment is primarily interested in maintaining the amateur model while keeping revenue flowing, at the expense of athletes’ educations.

“If ever there was a case of academic fraud, North Carolina would have to be the poster child — the longevity and the outrageous behavior to keep athletes eligible through systematic fraud,” said Gerald Gurney, a professor at the University of Oklahoma and past president of the Drake Group, which seeks to reform college athletics. “And it leads one to the absolute conclusion that this finding sanctions academic fraud among our institutions for the purpose of keeping athletes eligible.”

But others believe the N.C.A.A. made the proper decision because the organization is not designed to judge the legitimacy of individual institutions’ academic programs.

“I have never believed that a significant part of the N.C.A.A.’s governance and membership was comfortable with the N.C.A.A. coming in and saying, ‘We are going to determine what is an appropriate academic arrangement for athletes,’ because of the slippery slope it goes down,” said Tyrone P. Thomas, a lawyer at Mintz Levin who advises colleges and universities on N.C.A.A. matters.

“It’s a massive loophole,” he added, “and from the P.R. side it looks horrible — these athletes can do what they do, and it looks horrible. But guess what? Maybe that’s not the N.C.A.A.’s job. This is something the schools have always self-regulated.”

To those who wished the panel had punished North Carolina, the panel itself offered an implicit rejoinder, telling the “membership” — the association is made up of over 1,000 colleges and universities — that if it wished to condemn what happened at North Carolina, it needed to write such rules.

“It is more likely than not that student-athletes received fraudulent credit by the common understanding of what that term means,” the panel said. “It is also more likely than not that U.N.C. personnel used the courses to purposely obtain and maintain student-athletes’ eligibility. These strong possibilities, however, are not the operative or controlling starting points to the membership’s academic fraud analysis.

“What ultimately matters,” it added, “is what U.N.C. says about the courses.”

Correction:

A picture in an earlier version of this article was published in error. It showed North Carolina’s 2017 national championship team, not the 2005 championship team.

Kevin Draper contributed reporting.

A version of this article appears in print on , on Page D1 of the New York edition with the headline: N.C.A.A. Declines to Punish North Carolina for Academic Fraud. Order Reprints | Today’s Paper | Subscribe